Re: [PATCH] crypto: arm64/aes-ccm - Rewrite skcipher walker loop

[Tianjia Zhang <tianjia.zhang@linux.alibaba.com>]

Hi Herbert,

On 2/1/23 4:55 PM, Herbert Xu wrote:
> On Wed, Feb 01, 2023 at 10:53:37AM +0800, Tianjia Zhang wrote:
>>
>> 	while (walk.nbytes != walk.total) {
> 
> This is still buggy, because we can have walk.nbytes == 0 and
> walk.nbytes != walk.total.  You will enter the loop and call
> skcipher_walk_done which is not allowed.
> 
> That is why you should follow the standard calling convention
> for skcipher walks, always check for walk.nbytes != 0 and not
> whether the walk returns an error.
> 
> Cheers,

According to your previous reply, walker will ensure that the nbytes of
each iteration is at least the size of the chunk. If walk.nbytes == 0,
it must be the last chunk. If this is the case,
walk.nbytes == 0 && walk.nbytes != walk.total will not appear, sorry I
am not very clear about the details of walker, I don’t know if I
understand correctly.

Cheers,
Tianjia